python pip 错误 pkg_resources.DistributionNotFound

Question

我正在尝试安装一个新模块，但我发现这pip不起作用 - 它显示

pkg_resources.DistributionNotFound: The 'pip==1.5.6' distribution was not found and is required by the application

对于我执行的每个呼叫。另外，对于pip --help. 我发现一些建议pip使用pip或重新安装easy_install，但easy_install也不起作用：

pkg_resources.DistributionNotFound: The 'setuptools==5.7' distribution was not found and is required by the application

python有没有办法在不重新安装及其所有模块的情况下解决此问题？
我有 Linux Ubuntu 14.04。
apt-get install python-pip建议安装pip（以及一堆其他以下软件），就像我的系统中没有它一样。我害怕这样做，这里会发生冲突吗？

更新。
apt-get说它要安装以下内容：build-essential dpkg-dev fakeroot g++ g++-4.8 libalgorithm-diff-perl libalgorithm-diff-xs-perl libalgorithm-merge-perl libfakeroot libstdc++-4.8-dev python-chardet-whl python-colorama python-colorama-whl python-distlib python-distlib-whl python-html5lib python-html5lib-whl python-pip python-pip-whl python-requests-whl python-setuptools python-setuptools-whl python-six-whl python-urllib3-whl python-wheel。但据我所知，pip 在没有这些软件包的情况下为我工作。
我也表演了
which -a python:::/usr/bin/python
which -a pip/usr/local/bin/pip
python --versionPython 2.7.6

Answer 1

拥有错误的完整回溯将会很有用。可能导致此问题的一种情况是安装了多个版本的 Python。

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例如，在我的 Ubuntu 20.04.1 LTS 上，除了随 Ubuntu 20 分发的 Python 3.8 之外，我还从源代码安装了 Python 3.6。这就是我得到的结果pip3 --version安装 Python 3.6 后得到的结果：

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Traceback (most recent call last):\n  File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 581, in _build_master\n    ws.require(__requires__)\n  File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 898, in require\n    needed = self.resolve(parse_requirements(requirements))\n  File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 789, in resolve\n    raise VersionConflict(dist, req).with_context(dependent_req)\npkg_resources.VersionConflict: (pip 20.2.3 (/usr/local/lib/python3.6/site-packages), Requirement.parse(\'pip==20.0.2\'))\n\nDuring handling of the above exception, another exception occurred:\n\nTraceback (most recent call last):\n  File "/usr/bin/pip3", line 6, in <module>\n    from pkg_resources import load_entry_point\n  File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3126, in <module>\n    @_call_aside\n  File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3110, in _call_aside\n    f(*args, **kwargs)\n  File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3139, in _initialize_master_working_set\n    working_set = WorkingSet._build_master()\n  File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 583, in _build_master\n    return cls._build_from_requirements(__requires__)\n  File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 596, in _build_from_requirements\n    dists = ws.resolve(reqs, Environment())\n  File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 784, in resolve\n    raise DistributionNotFound(req, requirers)\npkg_resources.DistributionNotFound: The \'pip==20.0.2\' distribution was not found and is required by the application\n

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最后一行是有问题的错误，但请注意回溯中的一个重要细节：raise VersionConflict。

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这可以通过显式使用所需版本来解决pip：

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$ python3.6 -m pip --version\npip 20.2.3 from /usr/local/lib/python3.6/site-packages/pip (python 3.6)\n

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或者简单地：

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$ pip3.6 --version\npip 20.2.3 from /usr/local/lib/python3.6/site-packages/pip (python 3.6)\n

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人们可能会偶然发现的另一个问题是执行时缺少 lsb_release问题pip3.6 install问题：

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  File "/usr/local/lib/python3.6/subprocess.py", line 438, in run\n    output=stdout, stderr=stderr)\nsubprocess.CalledProcessError: Command \'(\'lsb_release\', \'-a\')\' returned non-zero exit status 1.\n

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这个问题可以通过定位来解决lsb_release.py，例如：

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sudo ln -s /usr/lib/python3/dist-packages/lsb_release.py /usr/local/lib/python3.6/site-packages/lsb_release.py\n

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现在可以升级\xc2\xa0pip3.6并安装新软件包：

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$ pip3.6 install --upgrade pip\n$ pip3.6 install mypy\n

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管理 Python 版本有不同的方法。小心使用类似的东西sudo update-alternatives --config python。更改系统的默认Python，可能会导致问题，包括终端无法打开等症状。最好有一个可用的备份终端，例如 Visual Studio Code 中的终端。

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